//! # libgoblin
//!
//! ![say the right
//! words](https://s-media-cache-ak0.pinimg.com/736x/1b/6a/aa/1b6aaa2bae005e2fed84b1a7c32ecb1b.jpg)
//!
//! `libgoblin` is a cross-platform trifecta of binary parsing and loading fun.  It supports:
//!
//! * An ELF32/64 parser, and raw C structs
//! * A 32/64-bit, zero-copy, endian aware, Mach-o parser, and raw C structs
//! * A PE32/PE32+ (64-bit) parser, and raw C structs
//! * A Unix archive parser and loader
//!
//! Goblin requires at least `rustc` 1.36.0, uses the 2018 rust edition, and is developed on stable.
//!
//! Goblin primarily supports the following important use cases:
//!
//! 1. Core, std-free `#[repr(C)]` structs, tiny compile time, 32/64 (or both) at your leisure
//!
//! 2. Type punning. Define a function once on a type, but have it work on 32 or 64-bit variants - without really changing anything, and no macros! See `examples/automagic.rs` for a basic example.
//!
//! 3. `std` mode. This throws in read and write impls via `Pread` and `Pwrite`, reading from file, convenience allocations, extra methods, etc. This is for clients who can allocate and want to read binaries off disk.
//!
//! 4. `Endian_fd`. A truly terrible name :laughing: this is for binary analysis like in [panopticon](https://github.com/das-labor/panopticon) which needs to read binaries of foreign endianness, _or_ as a basis for constructing cross platform foreign architecture binutils, e.g. [cargo-sym](https://github.com/m4b/cargo-sym) and [bingrep](https://github.com/m4b/bingrep) are simple examples of this, but the sky is the limit.
//!
//! # Example
//!
//! ```rust
//! use goblin::{error, Object};
//! use std::path::Path;
//! use std::env;
//! use std::fs;
//!
//! fn run () -> error::Result<()> {
//!     for (i, arg) in env::args().enumerate() {
//!         if i == 1 {
//!             let path = Path::new(arg.as_str());
//!             let buffer = fs::read(path)?;
//!             match Object::parse(&buffer)? {
//!                 Object::Elf(elf) => {
//!                     println!("elf: {:#?}", &elf);
//!                 },
//!                 Object::PE(pe) => {
//!                     println!("pe: {:#?}", &pe);
//!                 },
//!                 Object::Mach(mach) => {
//!                     println!("mach: {:#?}", &mach);
//!                 },
//!                 Object::Archive(archive) => {
//!                     println!("archive: {:#?}", &archive);
//!                 },
//!                 Object::Unknown(magic) => { println!("unknown magic: {:#x}", magic) }
//!             }
//!         }
//!     }
//!     Ok(())
//! }
//! ```
//!
//! # Feature Usage
//!
//! `libgoblin` is engineered to be tailored towards very different use-case scenarios, for example:
//!
//! * a no-std mode; just simply set default features to false
//! * a endian aware parsing and reading
//! * for binary loaders which don't require this, simply use `elf32` and `elf64` (and `std` of course)
//!
//! For example, if you are writing a 64-bit kernel, or just want a barebones C-like
//! header interface which defines the structures, just select `elf64`, `--cfg
//! feature=\"elf64\"`, which will compile without `std`.
//!
//! Similarly, if you want to use host endianness loading via the various `from_fd` methods, `--cfg
//! feature=\"std\"`, which will not use the `byteorder` extern crate, and read the bytes
//! from disk in the endianness of the host machine.
//!
//! If you want endian aware reading, and you don't use `default`, then you need to opt in as normal
//! via `endian_fd`

#![cfg_attr(not(feature = "std"), no_std)]

#[cfg(feature = "std")]
extern crate core;

#[cfg(feature = "alloc")]
#[macro_use]
extern crate alloc;

/////////////////////////
// Misc/Helper Modules
/////////////////////////

#[allow(unused)]
macro_rules! if_std {
    ($($i:item)*) => ($(
        #[cfg(feature = "std")]
        $i
    )*)
}

#[allow(unused)]
macro_rules! if_alloc {
    ($($i:item)*) => ($(
        #[cfg(feature = "alloc")]
        $i
    )*)
}

#[cfg(feature = "alloc")]
pub mod error;

pub mod strtab;

/// Binary container size information and byte-order context
pub mod container {
    pub use scroll::Endian;

    #[derive(Debug, Copy, Clone, PartialEq)]
    /// The size of a binary container
    pub enum Container {
        Little,
        Big,
    }

    impl Container {
        /// Is this a 64-bit container or not?
        pub fn is_big(self) -> bool {
            self == Container::Big
        }
    }

    #[cfg(not(target_pointer_width = "64"))]
    /// The default binary container size - either `Big` or `Little`, depending on whether the host machine's pointer size is 64 or not
    pub const CONTAINER: Container = Container::Little;

    #[cfg(target_pointer_width = "64")]
    /// The default binary container size - either `Big` or `Little`, depending on whether the host machine's pointer size is 64 or not
    pub const CONTAINER: Container = Container::Big;

    impl Default for Container {
        #[inline]
        fn default() -> Self {
            CONTAINER
        }
    }

    #[derive(Debug, Copy, Clone, PartialEq)]
    /// A binary parsing context, including the container size and underlying byte endianness
    pub struct Ctx {
        pub container: Container,
        pub le: scroll::Endian,
    }

    impl Ctx {
        /// Whether this binary container context is "big" or not
        pub fn is_big(self) -> bool {
            self.container.is_big()
        }
        /// Whether this binary container context is little endian or not
        pub fn is_little_endian(self) -> bool {
            self.le.is_little()
        }
        /// Create a new binary container context
        pub fn new(container: Container, le: scroll::Endian) -> Self {
            Ctx { container, le }
        }
        /// Return a dubious pointer/address byte size for the container
        pub fn size(self) -> usize {
            match self.container {
                // TODO: require pointer size initialization/setting or default to container size with these values, e.g., avr pointer width will be smaller iirc
                Container::Little => 4,
                Container::Big => 8,
            }
        }
    }

    impl From<Container> for Ctx {
        fn from(container: Container) -> Self {
            Ctx {
                container,
                le: scroll::Endian::default(),
            }
        }
    }

    impl From<scroll::Endian> for Ctx {
        fn from(le: scroll::Endian) -> Self {
            Ctx {
                container: CONTAINER,
                le,
            }
        }
    }

    impl Default for Ctx {
        #[inline]
        fn default() -> Self {
            Ctx {
                container: Container::default(),
                le: scroll::Endian::default(),
            }
        }
    }
}

/// Takes a reference to the first 16 bytes of the total bytes slice and convert it to an array for `peek_bytes` to use.
/// Returns None if bytes's length is less than 16.
#[allow(unused)]
fn take_hint_bytes(bytes: &[u8]) -> Option<&[u8; 16]> {
    bytes
        .get(0..16)
        .and_then(|hint_bytes_slice| hint_bytes_slice.try_into().ok())
}

#[derive(Debug, Default)]
/// Information obtained from a peek `Hint`
pub struct HintData {
    pub is_lsb: bool,
    pub is_64: Option<bool>,
}

#[derive(Debug)]
/// A hint at the underlying binary format for 16 bytes of arbitrary data
pub enum Hint {
    Elf(HintData),
    Mach(HintData),
    MachFat(usize),
    PE,
    Archive,
    Unknown(u64),
}

macro_rules! if_everything {
    ($($i:item)*) => ($(
        #[cfg(all(feature = "endian_fd", feature = "elf64", feature = "elf32", feature = "pe64", feature = "pe32", feature = "mach64", feature = "mach32", feature = "archive"))]
        $i
    )*)
}

if_everything! {

    /// Peeks at `bytes`, and returns a `Hint`
    pub fn peek_bytes(bytes: &[u8; 16]) -> error::Result<Hint> {
        use scroll::{Pread, LE};
        if &bytes[0..elf::header::SELFMAG] == elf::header::ELFMAG {
            let class = bytes[elf::header::EI_CLASS];
            let is_lsb = bytes[elf::header::EI_DATA] == elf::header::ELFDATA2LSB;
            let is_64 =
                if class == elf::header::ELFCLASS64 {
                    Some (true)
                } else if class == elf::header::ELFCLASS32 {
                    Some (false)
                } else { None };

            Ok(Hint::Elf(HintData { is_lsb, is_64 }))
        } else if &bytes[0..archive::SIZEOF_MAGIC] == archive::MAGIC {
            Ok(Hint::Archive)
        } else if (&bytes[0..2]).pread_with::<u16>(0, LE)? == pe::header::DOS_MAGIC {
            Ok(Hint::PE)
        } else {
            mach::peek_bytes(bytes)
        }
    }

    /// Peeks at the underlying Read object. Requires the underlying bytes to have at least 16 byte length. Resets the seek to `Start` after reading.
    #[cfg(feature = "std")]
    pub fn peek<R: ::std::io::Read + ::std::io::Seek>(fd: &mut R) -> error::Result<Hint> {
        use std::io::SeekFrom;
        let mut bytes = [0u8; 16];
        fd.seek(SeekFrom::Start(0))?;
        fd.read_exact(&mut bytes)?;
        fd.seek(SeekFrom::Start(0))?;
        peek_bytes(&bytes)
    }

    #[derive(Debug)]
    #[allow(clippy::large_enum_variant)]
    /// A parseable object that goblin understands
    pub enum Object<'a> {
        /// An ELF32/ELF64!
        Elf(elf::Elf<'a>),
        /// A PE32/PE32+!
        PE(pe::PE<'a>),
        /// A 32/64-bit Mach-o binary _OR_ it is a multi-architecture binary container!
        Mach(mach::Mach<'a>),
        /// A Unix archive
        Archive(archive::Archive<'a>),
        /// None of the above, with the given magic value
        Unknown(u64),
    }

    impl<'a> Object<'a> {
        /// Tries to parse an `Object` from `bytes`
        pub fn parse(bytes: &[u8]) -> error::Result<Object> {
            if let Some(hint_bytes) = take_hint_bytes(bytes) {
                match peek_bytes(hint_bytes)? {
                    Hint::Elf(_) => Ok(Object::Elf(elf::Elf::parse(bytes)?)),
                    Hint::Mach(_) | Hint::MachFat(_) => Ok(Object::Mach(mach::Mach::parse(bytes)?)),
                    Hint::Archive => Ok(Object::Archive(archive::Archive::parse(bytes)?)),
                    Hint::PE => Ok(Object::PE(pe::PE::parse(bytes)?)),
                    Hint::Unknown(magic) => Ok(Object::Unknown(magic))
                }
            } else {
                Err(error::Error::Malformed(format!("Object is too small.")))
            }
        }
    }
} // end if_endian_fd

/////////////////////////
// Binary Modules
/////////////////////////

#[cfg(any(feature = "elf64", feature = "elf32"))]
#[macro_use]
pub mod elf;

#[cfg(feature = "elf32")]
/// The ELF 32-bit struct definitions and associated values, re-exported for easy "type-punning"
pub mod elf32 {
    pub use crate::elf::dynamic::dyn32 as dynamic;
    pub use crate::elf::header::header32 as header;
    pub use crate::elf::note::Nhdr32 as Note;
    pub use crate::elf::program_header::program_header32 as program_header;
    pub use crate::elf::reloc::reloc32 as reloc;
    pub use crate::elf::section_header::section_header32 as section_header;
    pub use crate::elf::sym::sym32 as sym;

    pub mod gnu_hash {
        pub use crate::elf::gnu_hash::hash;
        elf_gnu_hash_impl!(u32);
    }
}

#[cfg(feature = "elf64")]
/// The ELF 64-bit struct definitions and associated values, re-exported for easy "type-punning"
pub mod elf64 {
    pub use crate::elf::dynamic::dyn64 as dynamic;
    pub use crate::elf::header::header64 as header;
    pub use crate::elf::note::Nhdr64 as Note;
    pub use crate::elf::program_header::program_header64 as program_header;
    pub use crate::elf::reloc::reloc64 as reloc;
    pub use crate::elf::section_header::section_header64 as section_header;
    pub use crate::elf::sym::sym64 as sym;

    pub mod gnu_hash {
        pub use crate::elf::gnu_hash::hash;
        elf_gnu_hash_impl!(u64);
    }
}

#[cfg(any(feature = "mach32", feature = "mach64"))]
pub mod mach;

#[cfg(any(feature = "pe32", feature = "pe64"))]
pub mod pe;

#[cfg(feature = "archive")]
pub mod archive;

#[cfg(test)]
mod tests {
    use super::*;
    if_everything! {
        #[test]
        fn take_hint_bytes_long_enough() {
            let bytes_array = [1; 32];
            let bytes = &bytes_array[..];
            assert!(take_hint_bytes(bytes).is_some())
        }

        #[test]
        fn take_hint_bytes_not_long_enough() {
            let bytes_array = [1; 8];
            let bytes = &bytes_array[..];
            assert!(take_hint_bytes(bytes).is_none())
        }
    }
}